The Holothurioidea (Echinodermata) collected during the Tyro Mauritania-II expedition 1988

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1 The Holothurioidea (Echinodermata) collected during the Tyro Mauritania-II expedition 1988 C. Massin Massin, C. The Holothurioidea (Echinodermata) collected during the Tyro Mauritania-II expedition 1988 Zool. Med. Leiden 67 (29), 24.xii.1993: , figs. 1-22, tables ISSN Key words: Holothurioidea; Mauritania; taxonomy; zoogeography. During the tyro Mauritania-II expedition (5-21.vi.1988) 15 holothurian species were collected between 19 and 1,900 m depth. Twelve species are new to the fauna of Mauritania, including Paracucumaria deridderae spec. nov. Mauritania represents the southern distribution limit of four species also known from Europe, and the northern distribution limit of five species also known from southern Africa. C. Massin, Royal Belgian Institute of Natural Sciences, Department of Invertebrates, 29 rue Vautier, 1040 Brussels, Belgium Introduction The Holothurioidea of Mauritania were described by Perrier (1902), Koehler & Vaney (1906), Herouard (1929) and Cherbonnier (1949b; 1972). So far 16 species have been reported, including 11 deep-sea species collected by the / Travailleur /, and the "Talisman" (Perrier 1902). The shallow-water fauna was poorly known, but the material of the Tyro Mauritania-II expedition, here described (table 1), fills this gap at least partly. The expedition took place during the period 5-21 June Sampling was mainly done on the continental shelf and slope between Cap Blanc and Cap limiris. Table 1: List of the species with stations, depth range (in m) and total number of specimens. Species Station numbers Depth range Total number of specimens Holothuria arguinensis MAU69,72,90, SHchopus regalis MAU 39,60,82,96,130,131, Paroriza pallens MAU Paelopatides grisea MAU Benthogone rosea MAU Cladodactyla senegalensis MAU Hemioedema gruveli MAU Panningia bispicula MAU Paracucumaria deridderae MAU ?Pseudocnus spec. MAU Stereoderma colochiriformis MAU Trachythyonefallax MAU 22,69,70,71,88, Phyllophorus pedinaequalis MAU 131,132,133, Echinocucumis tenera MAU 80, Labidoplax digitata MAU 77,78,86,

2 398 ZOOLOGISCHE MEDEDELINGEN 67 (1993) Material and methods Most of the holothurians were collected with Agassiz trawls of 1.2, 2.4, and 3.5 m opening and some with a van Veen grab. Collecting data are briefly presented in table 2. A full description of localities and sampling methods is given by van der Land (1988). The holothurians were sorted on board,fixed in 70% alcohol or in 10% formalin and later transferred to 70% alcohol. When a species was particularly abundant at a given station, Table 2. List of Tyro Mauritania-II stations wich yielded holothurians. AT = Agassiz trawl; FMS = fine muddy sand; HC = hard calcareous; MB = muddy bottom; MS = muddy sand; M+SG = mud + shell gravel; SMG = sandy mud gravel; WG = van Veen grab. Station Depth Position Bottom Gear Species Number of RMNH number inm specimens Ech.nr. MAU 'N-16 o 25'W MS AT Trachythyone fallax Stereoderma colochiriformis MAU / N / W MB AT Stichopus regalis MAU 'N-16 46'W - AT SHchopus regalis MAU / N-17 10'W MS WG Paracucumaria deridderae ? Pseudocnus spec MAU 'N / W MS AT Holothuria arguinensis Trachythyone fallax Panningia bispicula MAU / N-17 18'W MS AT Trachythyone fallax MAU / N / W MS AT Trachythyone fallax MAU / N-17 24'W MS AT Holothuria arguinensis MAU / N-17 09'W HC AT Cladodactyla senegalensis Hemioedema gruveli MAU 'N-17 o 17'W FMS WG Labidoplax digitata MAU / N-17 21'W FMS WG Labidoplax digitata MAU 'N-17 o 26'W - AT Echinocucumis tenera Trachythyone fallax MAU / N-17 30, W - AT Stichopus regalis MAU / N-16 52'W M+SG WG Labidoplax digitata MAU / N-16 54'W M+SG WG Labidoplax digitata MAU 'N 'W Mud AT Trachythyone fallax MAU 'N / W - AT Holothuria arguinensis MAU / N-17 02, W - AT Stichopus regalis MAU / N-16 48'W MS AT Holothuria arguinensis MAU 'N 'W SMG WG Echinocucumis tenera MAU 'N-17 o 06'W - AT Paroriza pallens Benthogone rosea MAU / N-17 44'W - AT Paelopatides cf. grisea MAU 'N-17 o 40'W MS AT Stichopus regalis MAU / N-17 41'W - AT Stichopus regalis Phyllophorus pedinaequalis MAU 'N / W - AT Phyllophorus pedinaequalis MAU 'N-17 o 48 / W - AT Phyllophorus pedinaequalis MAU 'N-17 o 48'W - AT Phyllophorus pedinaequalis MAU / N-17 39'W - AT Stichopus regalis

3 MASSIN: HOLOTHURIANS OF THE TYRO MAURITANIA-II EXPEDITION 399 only a few specimens were preserved. The bulk of the material is deposited in the collection of the Nationaal Natuurhistorisch Museum [NNM; formerly Rijksmuseum van Natuurlijke Historie (RMNH)], Leiden, The Nederlands. A few specimens of abundant species are now in the collections of the Royal Belgian Institute of Natural Sciences (IRSNB). Comparisons were made with material from the Museum National d'histoire Naturelle (MNHN, Paris, France), the Institute of Oceanographic Sciences (IOS, Wormley, U.K.) and the Royal Belgian Institute of Natural Sciences (IRSNB, Brussels, Belgium). Taxonomy Order Aspidochirotida Grube, 1840 Family Holothuriidae Ludwig, 1894 Genus Holothuria Linnaeus, 1767 Sub-genus Roweothuria Thandar, 1988 Holothuria (R.) arguinensis Koehler & Vaney, 1906 (fifrl) Holothuria arguinensis Koehler & Vaney, 1906: 62, pi. 5 figs. 5-13, pi. 6 figs ; Gruvel, 1909:1018; Herouard, 1925:7, fig. 6; Herouard, 1929:48, fig. 3A-K, pl 1 fig. 5. Holothuria (Holothuria) arguinensis; Panning, 1935:49, fig. 44. Holothuria (Lessonothuria) arguinensis; Rowe, 1969:149. Holothuria (Roweothuria) arguinensis; Thandar, 1988:48. Material. Mauritania: RMNH Ech (2 specimens); RMNH Ech (1 specimen); RMNH Ech (1 specimen); RMNH Ech (1 specimen). Descriptive notes. The general aspect, colour and ossicles (fig. 1) are in accordance with the description and figures given by Koehler & Vaney (1906) and Herouard (1929). The specimens were 160,150,137, 110 and 76 mm long and 95, 50, 65, 50 and 30 mm wide, respectively. These measurements are close to those given by Koehler & Vaney (1906) and Herouard (1929). Distribution. This shallow-water species (26-52 m), collected for the last time in 1929 (Herouard), is restricted to South Morocco and North Mauritania. Family Stichopodidae Haeckel, 1896 Genus Stichopus Brandt, 1835 Stichopus regalis (Cuvier, 1817) Synonymy. See Tortonese, 1965:66. Material. Mauritania: RMNH Ech (1 specimen); RMNH Ech (4 specimens); RMNH Ech (3 specimens); RMNH Ech (1 specimen); RMNH Ech (3 specimens); RMNH Ech (1 specimen); RMNH Ech (7 specimens). Descriptive notes. The specimens present no variation in comparison with material from the Mediterranean Sea (Tortonese 1965). Distribution. The depth distribution ( m) is in accordance with the data

4 400 ZOOLOGISCHE MEDEDELINGEN 67 (1993) Fig. 1. Holothuria (R.) arguinensis Koehler & Vaney, A: buttons of ventral body wall; B: tables of dorsal body wall; C: buttons of dorsal body wall. previously reported by Koehler (1921) for Atlantic specimens. Stichopus regalis is already known from the eastern Atlantic Ocean (Koehler 1921; Clark 1922; H&ouard 1929; Cherbonnier 1958b) south to Angola (Cherbonnier 1965a). This is the first record of the species from the coast of Mauritania where it appears as one of the most abundant species

5 MASSIN: HOLOTHURIANS OF THE TYRO MAURITANIA-II EXPEDITION 401 Family Gephyrothuridae Koehler & Vaney, 1905 Genus Paroriza H&ouard, 1902 Paroriza pallens (Koehler, 1896) (fig. 2) Stichopus pallens Koehler, 1896:11, pi. 1 fig. 1, pi. 4fig.45. Stkhopus (?) pallens; Perrier, 1902:287. Paroriza pallens; Heding, 1940:143; Sibuet, 1977:554; Khripounoff & Sibuet, 1980:22; Massin, 1987:117; Billet et al., 1988:423; Tyler et al., 1992:447. Material. Mauritania: RMNH Ech (1 specimen). 1 cm Fig. 2. Paroriza pallens (Koehler, 1896). Calcareous ring. R: radial piece; IR: interradial piece. Descriptive notes. The body is cylindrical, 75 mm in diameter and 195 mm long. The calcareous ring (fig. 2), the absence of ossicles, the gonad divided into two bundles on the right and left sides of the dorsal mesentery, the absence of tentacular ampullae and the presence of tube feet dorsally and ventrally, are characteristic of Paroriza pallens. Distribution. This is a deepsea species living on the upper part of the continental slope. So far it had only been reported from the eastern Atlantic, north of 44 N (Bay of Biscay, Porcupine Seabight). This is thefirstrecord from the coast of Mauritania. Family Synallactidae Ludwig, 1894 Genus Paelopatides Th el, 1886 Paelopatides cf. P. grisea Perrier, 1902 (fig. 3) Paelopatides grisea Perrier, 1902: 361; Heding, 1940:137; Billet et al., 1985: 407; Gage et al., 1985: 195; Harvey etal., 1988:183. Paelopatides gigantea; Sibuet, 1977:554. Material. Mauritania: RMNH Ech (4 specimens) (n.b. 35 specimens were collected at station MAU105 but only four specimens were preserved). Ireland: IOS (Discovery Collection) 50602#3 (2 specimens). Description. Skin abraded, torn and lacking any ossicles. No dorsal papillae distinguishable. Body flat, rounded at both ends (figs. 3A and B); the specimens are 230,198,180 and 153 mm long and 90,90,65 and 65 mm wide, respectively. Mouth

6 402 ZOOLOGISCHE MEDEDELINGEN 67 (1993) A B ^ 5mm Fig. 3. Paelopatides cf. P. grisea Perrier, A: ventral view; B: dorsal view; C: tentacle. ventral, anus dorsal. Skin gray-white, thick and gelatinous. Tentacle crown placed at some distance from anterior edge of body (fig. 3A). Tentacles in number, blackviolet. Each tentacle retractile, its stalk and tips made of a soft pliable disc with seven long finger-like processes (fig. 3C). Some processes bear secondary knobs.

7 MASSIN: HOLOTHURIANS OF THE TYRO MAURITANIA-II EXPEDITION 403 Mid-ventral tube feet small and retracted, in a zig-zag pattern, absent from the anterior third of the ventral sole. They appear as black-violet spots on the gray-white skin. Coelomic cavity very narrow. Five longitudinal muscles flat and close to each other, each as two broad bands. Two Polian vesicles. The right respiratory tree occupies the whole length of the coelomic cavity. All specimens had auto-eviscerated. Discussion. The general aspect of the body (fig. 3), the mid-ventral tube feet restricted to the posterior part of the body and the dorsal anus are characteristic of the genus Paelopatides Th6el, Although the four specimens lack ossicles, and their dorsal body wall was damaged, they fit well with the detailed description of Paelopatides grisea given by Perrier (1902,361). Distribution. The depth (1,900 m) at which the specimens were collected corresponds to the upper bathymetric limit of the species, where it is the most frequent according to Gage et al. (1985). P. grisea is a NE Atlantic species, known from Ireland to the Gulf of Guinea. This is the first record from the coast of Mauritania. Synonymy. See Hansen, 1975:48. Order Elasipodida Theel, 1882 Family Laetmogonidae Ekman, 1926 Genus Benthogone Koehler, 1896 Benthogone rosea Koehler, 1896 Material. Mauritania: RMNH Ech (7 specimens) (n.b. 41 specimens were collected at station MAU 104 but only seven specimens were preserved). Descriptive notes. Along the coast of Mauritania, Benthogone rosea is a well known and abundant deep sea species, previously collected by the "Travailleur" and "Talisman" (Perrier 1902). Distribution. It is a cosmopolitan species. Its bathymetrical range in the eastern Atlantic is 1,100-2,480 m (Hansen, 1975). Order Dendrochirotida Grube, 1840 Family Cucumariidae Ludwig, 1894 Genus Cladodactyla Brandt, 1835 Cladodactyla senegalensis Panning, 1940 (figs. 4,5) Cladodactyla senegalensis Panning, 1940: 172, figs. 5-7; 1949: 414, fig. 1; 1957: 29, figs ; Cherbonnier, 1950b: 476, figs. a-m. Material. Mauritania: RMNH Ech (2 specimens). Description. Both specimens are cylindrical, slightly curved with mouth and anus terminal. They are 17 and 48 mm long, and four and ten mm in diameter, respectively; ten dendritic tentacles, the two ventral smaller; tube feet restricted to the radii, especially numerous ventrally and more sparse dorsally.

8 404 ZOOLOGISCHE MEDEDELINGEN 67 (1993) 5 mm R 100nm Fig. 4. Cladodactyla senegalensis Panning, A: calcareous ring (R: radial piece; IR: interradial piece); B: ossicles of body wall; C: anal ossicles; D: rosettes of tentacles; E: rods and plates of tentacles.

9 MASSIN: HOLOTHURIANS OF THE TYRO MAURITANIA-II EXPEDITION 405 Fig. 5. Cladodactyla senegalensis Panning, Ossicles of tube feet. Calcareous ring of five radial and five interradial pieces without posterior projections; radial and interradial pieces are long, triangular and all of the same height (fig. 4A); one Polian vesicle; retractor muscles of the pharynx wide, flat, attached at the anterior third of the body length; gonad well developed in the larger specimen. Ossicles in the body wall scarce, small perforated plates (fig. 4B), larger near the anus (fig. 4C). Tube feet with straight or curved perforated rods and perforated plates (fig. 5). Tentacles with rods, numerous irregular perforated plates (fig. 4E) and some rare but characteristic rosettes (fig. 4D). Discussion. The specimens from Mauritania show no difference with the specimens from Dakar. Distribution. Cladodactyla senegalensis was previously known only from Dakar (Senegal). Genus Hemioedema Herouard, 1929 Hemioedema gruveli Herouard, 1929 (figs. 6,7) Hemioedema gruveli Herouard, 1929:45, fig. 2, pi. 1, fig. 4; Cherbonnier, 1958c: 321, figs. 1 and 2. Type material. MNHN 7013 (holotype and paratype: type locality Port Etienne, Mauritania). Other material. Mauritania: RMNH Ech (1 specimen). Description. Body contracted, nearly spherical, 40 mm in diameter; tube feet all over the body, more numerous ventrally than dorsally; radii visible only near the

10 Fig. 6. Hemioedema gruveli Herouard, A: calcareous ring (R: radial piece; IR: interradial piece); B: anal ossicles; C: ossicles of anal tube feet; D: ossicles of tube feet; E: rosettes of tube feet; F: rosettes of introvert.

11 MASSIN: HOLOTHURIANS OF THE TYRO MAURITANIA-II EXPEDITION 407 Fig. 7. Hemioedema gruveli Herouard, A: body wall ossicles; B: rods of tentacles; C: rosettes of tentacles. mouth; mouth and anus terminal. Body wall thin ( mm). Calcareous ring without posterior projections (fig. 6A); five radial and five interradial pieces of approximately the same height. Retractor muscles of the pharynx cylindrical, originating approximately at mid-body; ten dendritic tentacles; one Polian vesicle; gonad well developed. No ossicles in body wall except around the base of tube feet (fig. 7A) and near the anus. Anal ossicles large reticulated plates up to 230 im long, and star-shaped plates (fig. 6B). Tube feet with rods (180 to 250 im long) with perfotated extremities, and rosettes (fig. 6D); no terminal plates. Only a few rods with large perforated central process in the anal tube feet (fig. 6C). Tentacles with a few rods (50 to 230 jun long) (fig. 7B) and numerous rosettes (fig. 7C); the rosettes also present in the introvert (fig. 6F).

12 408 ZOOLOGISCHE MEDEDELINGEN 67 (1993) Discussion. Hemioedema gruveli Herouard, 1929, was known only from two type specimens in the collections of the MNHN. The material collected by the Tyro Mauritania-II expedition is very similar to the type material, except for the thickness of the body wall: mm for the collected specimen versus over five mm for the type specimens (all the specimens are strongly contracted). Distribution. This species is limited to Mauritania. The known distribution of the genus Hemioedema is also restricted, from Gabon to Mauritania (Herouard, 1929; Cherbonnier 1949a, 1950a, 1957,1958c, 1965a, 1973). Three of fhe four known species viz. H. gruveli, H. aibofusca Cherbonnier, 1949, and H. multipodia Cherbonnier, 1973, so far only have been collected at the type locality. The fourth one, H. goreensis Cherbonnier, 1949, is known from Gabon, Sierra Leone and Senegal. Genus Paracucumaria Panning, 1949 Paracucumaria deridderae spec. nov. (figs. 8-10) Material. Mauritania: RMNH Ech (23 specimens) (the specimen labelled 05826/5 is designated as holotype). Description. All specimens are fragmented. The number of 23 specimens corresponds to the number of anterior ends with a calcareous ring. Small holothurians (estimated mm long), cylindrical with mouth and anus terminal. Tube feet restricted to radii, in two rows, evenly distributed along body length. Ten tentacles, the two ventral ones smaller. Calcareous ring thin with triangular radial and interradial pieces (fig. 8A); both pieces with deep posterior notch delimiting short posterior projections (fig. 8B). Retractor muscles of the pharynx thick and short; one long Polian vesicle; short and narrow stone canal ends in a small bean-shaped madreporic plate (fig. 8C). Body wall with one ossicle type, viz. large elongate knobbed perforated plates. Those from the anterior body wall are jjm long and jxm wide, and knobbed at one extremity (fig. 8D). The posterior plates are longer ( [xm) and wider ( \im), and their knobbed extremity is also spiny (fig. 8E). Tube feet contain irregular perforated rods with a central perforated process (fig. 9B); large central processes are knobbed and as a consequence, the rods appear as knobbed plates (fig. 9B). Ossicles of posterior tube feet (fig. 10A) larger than ossicles of anterior tube feet (fig. 9B). In the introvert occur scarce small ( \\m long), knobbed, perforated plates, sometimes with spines (fig. 9A). Tentacles with large, massive V-shaped or straight rods ( Lim long)(fig. 10B) located in the stem and short (40-90 xm long), thin, more or less straight rods located at the tips (fig. 10C). Discussion. Three species of Paracucumaria are known from the NE Atlantic Ocean: Paracucumaria hyndmani (Thompson, 1840), P. mauntanica (Herouard, 1929) and P. thalassae Cherbonnier, P. mauritanica and P. thaiassae are readily distinguished from P. deridderae spec. nov. because they have numerous small ( \\m long) perfo-

13 MASSIN: HOLOTHURIANS OF THE TYRO MAURITANIA-II EXPEDITION 409 Fig. 8. Paracucumaria deridderae spec. nov. A: calcareous ring, dorsal pieces; B: calcareous ring, ventral pieces (R: radial piece; IR: interradial piece); C: stone canal with madreporic plate; D: large plates of anterior body wall; E: large plates of posterior body wall.

14 410 ZOOLOGISCHE MEDEDELINGEN 67 (1993) Fig. 9. Paracucumaria deridderae spec. nov. A: ossicles of introvert; B: ossicles ot anterior tube feet. rated plates (with 2-5 perforations) in the body wall, whereas in P. deridderae the plates are longer ( im) with more numerous perforations (10-18). P. deridderae is close to P. hyndmani, whose ossicles show great variation. Madsen (1942) distinguished two subspecies of P. hyndmani: P. hyndmani robusta (Madsen, 1942) from England, and P. hyndmani typica (Madsen, 1942) from Scandinavia. The body wall plates of P. hyndmani robusta are rounded, thick, smooth plates, with the perforations often obliterated (Madsen 1942; personal observation on the holotype and on material from Spain and the Bay of Biscay). This is quite different from P.

15 MASSIN: HOLOTHURIANS OF THE TYRO MAURITANIA-II EXPEDITION 411 Fig. 10. Paracucumaria deridderae spec. nov. A: ossicles of posterior tube feet; B: large rods of tentacles; C: small rods of tentacles. deridderae which has elongated, knobbed body wall plates with well defined perforations. Some specimens of P. hyndmani typica show body wall plates very similar to P. deridderae. However, P. deridderae differs from P. hyndmani typica by: 1. the absence of smooth plates with large perforations, 2. the presence of spiny knobbed plates in the

16 412 ZOOLOGISCHE MEDEDELINGEN 67 (1993) Fig. 11. Pseudocnus spec. Ossicles of posterior tube feet. body wall, 3. the presence of knobbed plates and knobbed rods in the tube feet. Etymology. The species is named after Dr. Chantal De Ridder who sorted the material on board. Genus Pseudocnus Panning, 1949? Pseudocnus spec, (figs. 11,12) Material. Mauritania: RMNH Ech (1 specimen). Description. A small holothurian (approximately 41 mm long), slightly U- shaped, with the body tapering anteriorly and posteriorly. Mid-ventral diameter 13 mm; posterior and anterior diameter 4-5 mm. No calcareous ring, no tentacles and no introvert because the specimen is eviscerated. Tube feet numerous, restricted to the radii, dorsally and ventrally, in double rows; mid-ventrally, four rows of tube feet. Skin rigid because of numerous plates. In the skin two kinds of ossicles. Anteriorly, large, very thick knobbed perforated plates im long (fig. 12A), rounded or oval with 2-10 perforations. Posteriorly, large, smooth thick perforated plates ( Jim long) with knobs and spines at one end (fig. 12B). Anterior tube feet with perforated rods more or less straight, nm long (fig. 12C). Posterior tube feet with irregular V-shaped rods ( Jim long) (fig. 11) and irregular knobbed plates ( pm long) (fig. 11). Discussion. General shape and ossicles of this specimen are suggestive of the genus Pseudocnus Panning, 1949, and resemble the South African Pseudocnus dubiosus africanus (Britten 1910) (see Panning, 1962: 64, figs. 8 and 9). However, the absence of tentacles, calcareous ring and introvert do not allow identification of the present specimen to the generic level with any confidence.

17 MASSIN: HOLOTHURIANS OF THE TYRO MAURITANIA-II EXPEDITION 413 Fig. 12. Pseudocnus spec. A: ossicles of anterior body wall; B: ossicles of posterior body wall; C: rods of anterior tube feet. Genus Stereoderma Ayres, 1851 Stereoderma colochiriformis (Ludwig & Heding, 1935) (% 13) Cucumaria kirschbergi var. colochiriformis Ludwig & Heding, 1935:169, figs Stereoderma colochiriformis; Cherbonnier, 1957:487, fig. 1; Cherbonnier, 1965b: 648. Material. Mauritania: RMNH Ech (1 specimen).

18 414 ZOOLOGISCHE MEDEDELINGEN 67 (1993) Fig. 13. Stereoderma colochiriformis (Ludwig & Heding, 1935). A: calcareous ring (R: radial piece; IR: interradial piece); B: stone canal with madreporic plate; C: plates of body wall; D: plates of dorsal papillae; E: end plate of tube foot; F: ossicles of ventral tube feet.

19 MASSIN: HOLOTHURIANS OF THE TYRO MAURITANIA-II EXPEDITION 415 Description. Body U-shaped, 65 mm long, pentagonal, tapering at both ends; colour in alcohol gray-white with brown-red spots; skin thin, rigid because of numerous ossicles; tube feet and dorsal papillae bristling with spines of the ossicles; ventral podia restricted to the radii, in two rows. Dorsal papillae scarce, arranged in one row in a zig-zag pattern along the radii. Calcareous ring without posterior projections (fig. 13A), thin and fragile; radial pieces with a small notch on the anterior tooth and somewhat higher than the interradial pieces (fig. 13A). Retractor muscles of the pharynx short, thin, round, originating at the anterior V6 of the body length; one Polian vesicle; one short and narrow stone canal, the madreporic plate convoluted (fig. 13B). Ossicles from body wall nodulous perforated plates ( im long) sometimes with one long or several short spines (fig.l3c); ventral tube feet with nodulous perforated plates, most of them bearing a strong spine at one extremity (fig. 13F); ventral tube feet also with rods (fig. 13F) and a very characteristic pentagonal end plate (fig. 13E). Dorsal papillae with nodulous perforated plates (fig. 13D) similar to those of the ventral tube feet. Discussion. The specimen from Mauritania is very similar to the specimen from Sierra Leone described by Cherbonnier (1957), differing only in the presence of end plates in the tube feet. Distribution. Stereoderma colochiriformis is a tropical West African species (Zaire, Togo, Sierra Leone) collected up to now between 44 and 80 m. The present record from Mauritania extends the known northern distribution limit considerably. Genus Trachythyone Studer, 1876 Trachythyone fallax Cherbonnier, 1958 (figs ) Trachythyone fallax Cherbonnier, 1958a: 101, fig. 3; Cherbonnier, 1965a: 6; Cherbonnier, 1965b: 648. Type material MNHN (ossicles from holotype; type locality Sierra Leone / N 17 10'W). Other material Mauritania: RMNH Ech (1 specimen); RMNH Ech (2 specimens); RMNH Ech (1 specimen); RMNH Ech (1 specimen); RMNH Ech (2 specimens); RMNH Ech (1 specimen). Cameroun: MNHN (ossicles) (1 specimen). Cabinda: IRSNB IG20403 (2 specimens). Description. Small U-shaped or S-shaped holothurian (24-41 mm); body tapering at both ends with mouth and anus terminal. Skin thin, rigid because of numerous ossicles. Podia scarce, short, rigid, in a single zig-zag row along radii; mid-ventrally, longer and in a double row. Calcareous ring thin, fragile with radial pieces higher than interradial pieces; both pieces with deep anterior notch (fig. 14A). Retractor muscles of pharynx slender and short. Two kinds of ossicles in the body wall: in the upper layer, small baskets (45-55 \xm in diameter) derived from a primary cross and with 4-8 peripheral short rounded spines (fig. 15A); in the deeper layer, large perforated plates (fig. 14B) up to 700 pm long and 350 Jim wide. At base of tube feet, long (up to 420 pm), narrow perforated plates, sometimes curved (fig. 15B); near apex of tube feet, small curved rods ( xm long) with perforated extremities (fig. 16A), irregular plates (fig. 16A) and

20 416 ZOOLOGISCHE MEDEDELINGEN 67 (1993) Fig. 14. Trachythyone fallax Cherbonnier, A: calcareous ring (R: radial piece; IR: interradial piece); B: large plates of body wall.

21 MASSIN: HOLOTHURIANS OF THE TYRO MAURITANIA-II EXPEDITION 417 Fig. 15. Trachythyone fallax Cherbonnier, A: cups of body wall; B: large plates of tube feet. baskets (fig. 16B) identical to those of body wall. Tentacles with large rods ( im long) in stalk (fig. 16C) and small rods (40-80 \xm long) at tips (fig. 16D); both rods with peforated tips. Discussion. The specimens from Mauritania closely resemble the type material from Sierra Leone. However, the species is variable; specimens from e.g. Cameroun and Cabinda have thinner and smoother perforated plates in the body wall. Distribution. The species is known from Cabinda, Dahomey, Cameroun and Sierra Leone. This find of T. fallax represents the first record of this species for Mauritania and an extension of its known northern distribution limit just as for Stereoderma colochiriformis.

22 418 ZOOLOGISCHE MEDEDELINGEN 67 (1993) ARD 1 0 ^ m Fig. 16. Trachytthyone fallax Cherbonnier, A: rods and plates of tube feet. B: cups of tube feet; C: large rods of tentacles; D: small rods of tentacles.

23 MASSIN: HOLOTHURIANS OF THE TYRO MAURITANIA-II EXPEDITION 419 Family Phyllophoridae Oestergren, 1907 Genus Phyllophorus Grube, 1840 Sub-genus Phyllophorus Grube, 1840 Phyllophorus (P.) pedinaequalis Cherbonnier, 1969 (figs. 17,18) Phyllophorus pedinaequalis Cherbonnier, 1969:357,fig. 5; Cherbonnier 1970:1267. Type material. MNHN (ossicles from holotype and paratypes: type locality Bay of Biscay 43 53'1N 08 42'2W). Other material Mauritania: RMNH Ech (25 specimens); RMNH Ech (5 specimens); RMNH Ech (11 specimens); RMNH Ech (9 specimens). Description. Body U-shaped, cylindrical, slightly tapering anteriorly and strongly posteriorly; anus and mouth terminal; skin soft, thin, translucent in extended specimens; body mm long and 5-12 mm in diameter; tube feet all over body, no radii visible. Anus surrounded by five large anal papillae. Tentacles in two concentric crowns; external crown with large tentacles and internal crown with 4-5 small tentacles. Calcareous ring with five radial and five interradial pieces; radial pieces much longer than interradial (fig. 18A); interradial pieces triangular (fig. 18A); radial pieces rectangular with posterior short projections and anterior notches (one large central and two small lateral) (fig. 18A). One Polian vesicle; one short stone canal terminating in a morula shape madreporic plate (fig. 18B). Retractor muscles of pharynx originating in anterior fourth of body length. No ossicles in body wall except arround anus; anal ossicles large tables (fig. 18C); table disk perforated by 8 to 12 large central holes and smaller peripheral holes; edge of disk sinuous and nodulous; four pillars with two transverse beams; pillars end in Fig. 17. Phyllophorus (P) pedinaequalis Cherbonnier, Rods of tentacles

24 420 ZOOLOGISCHE MEDEDELINGEN 67 (1993) C D E _ l 0 0 M L m Fig. 18. Phyllophorus (P.) pedinaequalis Cherbonnier, A: calcareous ring (R: radial piece; IR: interradial piece); B: stone canal with madreporic plate; C: tables of body wall; D: end plate of tube foot; E: rosettes of introvert. a crown of short spines. Large rosettes in introvert (fig. 18E). Tube feet without ossicles, except for a large terminal plate (fig. 18D). Two kinds of rods in tentacles: 1. thin and smooth curved rods ( \im long) with sharp tips (fig. 17); 2. thick and smooth curved rods ( [im long) with enlarged, nodulous tips (fig. 17). Discussion. The specimens from Mauritania are similar to those described by Cherbonnier (1969) from the Bay of Biscay. Distribution. The species hitherto was only known from the Bay of Biscay

25 MASSIN: HOLOTHURIANS OF THE TYRO MAURITANIA-II EXPEDITION 421 (Spain, Galicia). It appears to be locally abundant along the coast of Mauritania. The species is typical of the upper part of the continental slope ( m). Family Ypsilothuridae Heding, 1942 Genus Echinocucumis Sars, 1859 Echinocucumis tenera Cherbonnier, 1958 (% 19) Echinocucumis tenera Cherbonnier 1958a: 103, fig. 4; 1965a: 8, pi 2 fig. f-j. Type material. MNHN (ossicles from holotype: type locality Sierra Leone 14 21'N 8 23'W). Other material. Mauritania: RMNH Ech (2 specimens); RMNH Ech (1 specimen). Cabinda: IRSNB IG20403 (10 specimens). Description. Small U-shaped holothurians (27-47 mm long, and maximally 6 mm in diameter) with body tapering anteriorly and posteriorly (fig. 19A). Tube feet scarce, restricted to radii (fig. 19A), more numerous ventrally than dorsally with maximum density in middle of body. Calcareous ring (fig. 19B) and ossicles of body wall (fig. 19C) similar to those of holotype. Ossicles of tube feet curved rods with perforated tips and sometimes with enlarged perforated central part (fig. 19E); end plate of tube feet small with four large central holes (fig. 19D). Two kind of rods in tentacles: large rods ( pm long) in stalk (fig. 19F), and small rods ( \xm long) in tips (fig. 19G). Discussion. The specimens from Mauritania differ only in details from those from Cabinda and Sierra Leone. There are no large plates with curved spines in the body wall as described by Cherbonnier (1965a: pi. 2 figs, i-j) from Cabinda specimens, and no central perforated process on the tentacle rods as decribed by Cherbonnier (1958a; fig. 4h) from the Sierra Leone specimen. Distribution. Echinocucumis tenera was known from Cabinda and Sierra Leone. So far the species had not been reported from Mauritania, the present record extending the known distributional range considerably to the north. Genus Panningia Cherbonnier, 1958 Panningia bispicula Cherbonnier, 1964 (figs. 20,21) Panningia bispicula Cherbonnier, 1964: 533; Cherbonnier, 1965a: 9, pi. 3 figs, a-o; Cherbonnier, 1965b: 653, fig. 3a-b, fig. 4a-p. Tpe material. IRSNB IG16808 (holotype: type locality Zaire 4 48'S 11 41'E; syntype). Other material. Mauritania: RMNH Ech (1 specimen). Zaire: IRSNB IG20403 (4 specimens). Description. Small holothurian (26 mm long), S-shaped, with the body tapering at both ends (fig. 20A). Mouth and anus terminal. Skin thin and rigid because of numerous large plates. Tube feet restricted to radii, scarce dorsally, more abundant mid-ventrally (fig. 20A).

26 422 ZOOLOGISCHE MEDEDEUNGEN 67 (1993) Fig. 19. Eehinocucumis tenera Cherbonnier, A: general view; B: calcareous ring (R radial piece; IR: interradial piece); C: large plates of body wall; D: end plate of tube foot; E: rods of tubefeet;f: large rods of tentacles; G: small rods of tentacles.

27 MASSIN: HOLOTHURIANS OF THE TYRO MAURUANIA-H EXPEDITION 423 Fig. 20. Panningia bispicula Cherbonnier, A: general view; B: calcareous ring (R: radial piece; IR: interradial piece); C: large plates of body wall; D: X-shaped ossicles of body wall; E: ossicles of dorsal tube feet; F: end plate of dorsal tube foot; G: ossicles of ventral tube feet; H: end plate of ventral tube foot.

28 424 ZOOLOGISCHE MEDEDELINGEN 67 (1993) Fig. 21. Panningia bispicula Cherbonnier, Ossicles of tentacles. A: large rods; 6: spiny curved plates; C: irregular rods; D: rosettes. Calcareous ring thin, fragile, made of ten pieces. Radial and interradial pieces of same height, without posterior projections but with deep posterior notch (fig. 20B); radial pieces with deep central groove for insertion of retractor muscles of pharynx. Retractor muscles very thick and short. One type of ossicle in body wall: large perforated plates with knobs at one tip and a sharp perforated point bending with an angle of 60 to 90 (fig. 20C). These plates ( nm long) derive from X-shaped ossicles (fig. 20D). Dorsal and ventral tube feet with curved rods bearing strong central tooth (figs. 20E and G); the teeth

29 MASSIN: HOLOTHURIANS OF THE TYRO MAURTTANIA-H EXPEDITION 425 protrude through the skin, giving the tube feet a spiny surface. In ventral tube feet, these strong spines are sometimes divided into two irregular processes (fig. 20G); very small perforated end plates (figs. 20F and H). Tentacles with numerous ossicles; large rods ( Jim long) with perforated tips (fig. 21A), spiny curved plates ( [im long) (fig. 21B), small irregular rods ( \im long) (fig. 21C) and rosettes (fig. 21D). Discussion. The specimen from Mauritania shows no differences from the type material from Zaire (Cherbonnier, 1964,1965a) and from the material from Dahomey (Cherbonnier, 1965b). Distribution. Panningia bispicula was known from Zaire and Dahomey. The species is new to the fauna of Mauritania, extending its known distribution much further north. Synonymy. See Tortonese, 1965:106. Order Apodida Brandt, 1835 Family Synaptidae Burmeister, 1837 Genus Labidoplax Oestergren, 1898 Labidoplax digitata (Montagu, 1808) (% 22) Material. Mauritania: RMNH Ech (3 specimens); RMNH Ech (1 specimen); RMNH Ech (3 specimens); RMNH Ech (4 specimens). Descriptive notes. Body shape, tentacles and ossicles (fig. 22) of the specimens are characteristic of Labidoplax digitata (Montagu, 1808). Thirteen specimens are intact. Their length varies from 13 to 52 mm. Distribution and habitat. The depth range observed (35-65 m) corresponds to the upper limit of the species (Koehler 1921; Tortonese 1965; Cherbonnier 1969,1970). L. digitata lives deep in the muddy sand. This explains why 16 of the 17 specimens were collected with a van Veen grab. This species is common in Europe (Atlantic coast and Mediterranean Sea) and is very abundant along the coast of Morocco (Herouard 1929). Its occurence in Mauritania represent its southernmost distribution limit. This is the first record of this species for Mauritania. Zoogeographical comments The holothurian fauna of Mauritania now includes 28 species which can be divided into five groups (excluding Pseudocnus spec). 1. Species restricted to Mauritania, or almost so (sometimes extending to North Senegal and South Morocco): Holothuria arguinensis Koehler & Vaney, 1906; Thyone basescoi Cherbonnier, 1972; Paracucumaria mauritanica (Herouard, 1929); Paracucumaria deridderae spec, nov.; Hemioedema gruveli Herouard, 1929; Molpadia loricata Perrier, Species also known from Europe and the Mediterranean Sea, for which Mauri-

30 426 ZOOLOGISCHE MEDEDELINGEN 67 (1993) Fig. 22. Labidoplax digitata (Montagu, 1808). A: anchor of body wall; B: plates of body wall; C: ossicles of tentacles. tania is the southern distribution limit: Paroriza pallens (Koehler, 1896); Ocnus planci Brandt, 1835; Phyllophorus pedinaequalis Cherbonnier, 1969; Labidoplax digitata (Montagu, 1808). 3. West African species for which Mauritania is the northern distribution limit: Cladodactyla senegalensis Panning, 1940; Stereoderma colochiriformis (Ludwig & Heding, 1935); Trachythyone fallax Cherbonnier, 1958; Echinocucumis tenera Cherbonnier, 1958; Panningia bispicula Cherbonnier, Deep-sea species with at least an Atlantic distribution (some of them being cosmopolitan): Mesothuria verillii (Theel, 1886); Benthothuria funebris Perrier, 1902; Bathyplotes tizardi Th^el, 1882; Bathyplotes reptans Perrier, 1902; Paelopatides cf. P. grisea

31 MASSIN: HOLOTHURIANS OF THE TYRO MAURITANIA-II EXPEDITION 427 Perrier, 1902; Benthodytes lingua Perrier, 1902; Benthogone rosea Koehler, 1896; Laetmogone violacea Theel, 1879; Ypsilothuria talismani Perrier, 1902; Ypsilothuria attenuata Perrier, Species with a wide bathymetrical range and with at least an eastern Atlantic distribution: Stichopus regalis (Cuvier, 1817); Molpadia musculus Risso, The holothurian fauna of the coast of Mauritania is still imperfectly known. More collecting needs to be done, and more species are to be expected. Nevertheless, the material collected during the Tyro Mauritania-II expedition, coupled with data from the literature show that Mauritania forms the southern extreme distribution limit for some European species and the northern distribution limit for some tropical African species. The zoogeographical "hinge" position of Mauritania, here observed for the Holothurioidea, was already known for other groups of pelagic or benthic animals (see Ekman 1953; Briggs 1974). In fact, Mauritania is known as the border between the Atlantico-Mediterranean fauna (Lusitanian Province) and tropical African fauna (West African Province). This phenomenon is linked to the fact that tropical Atlantic waters and temperate Atlantic waters mix between Cap Blanc and Cap Verde. Acknowledgements It is a pleasure to thank Dr. Ch. De Ridder who invited me to study the holothurians collected during the RMNH Tyro Mauritania-II expedition kindly made available by the NNM, Leiden; Dr. D. Pawson, Dr. P. Willenz and Mr. S. De Grave for critically reading the manuscript and improving upon the English; Mrs. P.A.6. Jackson (IOS) for the loan of material; Dr. N. Cominardi for welcoming me in the Laboratoire des Invertebres Marins et Malacologie at the MNHN. Figures 2 and 3 are by Mr. H. Van Paesschen. References Billet, D.S.M., B. Hansen & Q.J. Hoggett, Pelagic Holothurioidea (Echinodermata) of the northeast Atlantic. In: Keegan B.F. & B.D.S. O'Connor (eds.). Echinodermata. Proc. 5th Int. Echinoderm Conf., Galway: Rotterdam. Billet, D.S.M., C. Llewellyn & J. Watson, Are deep-sea holothurians selective feeders? In: Burke, R.D., P.V. Mladenov, P. Lambert & R.I. Parsley (eds.). Echinoderm biology. Proc. 6th Int. Echinoderm Conf., Victoria: Rotterdam. Briggs, J.C., Marine Zoogeography: New York. Cherbonnier, G., 1949a. Note sur une holothurie nouvelle des cotes du Senegal: Hemioedema goreensis n. sp. Bull. Mus. nat. Hist. nat. Paris, ser. 2,21: Cherbonnier, G., 1949b. Note sur une holothurie dendrochirote des cdtes de Mauritania Cucumaria mauritanica. Bull. Mus. nat. Hist. nat. Paris, ser. 2,21: Cherbonnier, G., 1950a. Sur la presence au Gabon de Hemioedema goreensis. Bull. Mus. natn. Hist. nat. Paris, ser. 2,22 (3): 378. Cherbonnier, G., 1950b. Note sur une holothurie dendrochitote de Dakar: Cladodactyla senegalensis Panning. Bull. Mus. natn. Hist. nat. Paris, ser. 2,22: Cherbonnier, G., Holothuries des cotes de Sierra Leone. Bull. Mus. natn. Hist. nat. Paris, ser. 2, 29: Cherbonnier, G., 1958a. Holothuries de cotes de Sierra Leone (2e note). Bull. Mus. natn. Hist. nat. Paris, ser. 2,30:

32 428 ZOOLOGISCHE MEDEDELINGEN 67 (1993) Cherbonnier, G., 1958b. Holothuries des cotes de Sierra Leone (5e et dern. note). Bull. Mus. natn. Hist. nat. Paris, ser. 2,30: Cherbonnier, G., 1958c. Le genre Hemioedema. Bull. Inst.fr. Afr. noire 20A: Cherbonnier, G Note preliminaire sur les holothuries de ratlantique sud. Bull. Mus. natn. Hist. nat. Paris, ser. 2,36 (4): Cherbonnier, G., 1965a. Expedition oceanographique beige dans les eaux coheres africaines de l'atlantique sud ( ): holothurides. Inst. r. Sci. nat. Belg. 3 (11): Cherbonnier, G., 1965b. Holothuries recoltees par A. Crosnier dans le Golfe de Guinee. Bull. Mus. natn. Hist. nat. Paris, ser. 2,36: Cherbonnier, G., Echinodermes recoltes par la Thalassa au large des cotes ouest de Bretagne et du Golfe de Gascogne (3-12 aoiit 1967). Bull. Mus. natn. Hist. nat. Paris, ser. 2,41 (1): Cherbonnier, G., Echinodermes recoltes par la Thalassa au large des cotes d'espagne et du Golfe de Gascogne. Bull. Mus. natn. Hist. nat. Paris, ser. 2,41 (5): Cherbonnier, G., Thyone bacescoi, nouvelle espece d'holothurie dendrochirote (Echinodermata) des cdtes de Mauritanie. Bull. Mus. natn. Hist. nat. Paris, Zool, ser. 3,30 (24): Cherbonnier, G., Sur une nouvelle espece d'holothurie dendrochirote du golfe de Guinee: Hemioedema multipodia. Bull. Mus. natn. Hist. nat. Paris, Zool. 115 (170): Clark, H.L., The holothurians of the genus Stichopus. Bull. Mus. comp. Zool. Harv. 65 (3): Ekman, S., Zoogeography of the Sea: London. Gage, J.D., D.S.M. Billet, M. Jensen & P.A. Tyler, Echinoderms of the Rockall Trough and adjacent areas. 2. Echinoidea and Holothurioidea. Bull. Br. Mus. (nat. Hist.) Zool. 48 (4): Gruvel, A., Dispersion de quelques especes appartenant a la faune marine des cotes de Mauritanie. C. r. hebd. Seanc. Acad. Sci Paris 149: Hansen, B., Systematics and biology of deep-sea holothurians. Part I. Elasipoda. Galathea Rep. 13: Harvey, R., J.D. Gage, D.S.M. Billet, A.M. Clark & G.L.J. Paterson, Echinoderms of the Rockall Trough and adjacent areas. 3. Additional records. Bull. Br. Mus. (nat. Hist.) Zool. 54 (4): Heding, S., Die Holothurien der Deutschen Tiefsee-Expedition. II. Aspidochirote und Elasipode Formen. Wiss. Ergebn. dt. Tiefsee-Exped. Valdivia 24 (3): Herouard, E., Sur la stereometrie des corpuscules calcaires et leurs rapports avec l'elat mesomorphe de la matiere. Bull. Inst, oceanogr. Monaco 464:1-14. Herouard, E., Holothuries de la cote atlantique du Maroc et de Mauritanie. Bull. Soc. Sci. nat. Maroc9(l-6): Khripounoff, A. & M. Sibuet, La nutrition d'echinodermes abyssaux. I. Alimentation des holothuries. Mar. Biol. 60: Koehler, R., Resultats scientifiques de la campagne du "Caudan" dans le Golfe de Gascogne. Echinodermes. Ann. Univ. Lyon 26: Koehler, R., Faune de France. 1. Echinodermes: Paris. Koehler, R. & C. Vaney, Mission des pecheries de la cote occidentale d'afrique. II. Echinodermes. Act. Soc. linn. Bordeaux 60: Land, J. van der, Shipboard report of the Tyro Mauritania-II Expedition 1988:1-36,8 figs. Ludwig, H. & S. Heding, Die Holothurien der Deutschen Tiefsee-Expedition. I. Fusslose und dendrochiroten Formen. Wiss. Ergebn. dt. Tiefsee-Exped. Valdivia 24 (2): Madsen F. J., Cucumaria hyndmani. The variation of its calcareous deposits. Vidensk. Meddr. denks naturh. Foren. 105: Massin, CL, Holothuries nouvelles et peu connues recoltees en Indonesie au cours de la Snellius- II Expedition. Bull. Inst. r. Sci. nat. Belg. Biol. 57: Panning, A., Die Gattung Holothuria. II. Mitt. zool. Staatinst. Zool. Mus. Hamburg 45: Panning, A., Dendrochirote Holothurien von Dakar. 'Vidensk. Meddr. densk naturh. Foren. 104: Panning, A., Versuch einer Neueordnung der Familie Cucumariidae (Holothurioidea, Dendrochirota). Zool. Jahrb. 78: Panning, A., Bemerkungen iiber die Holomurien-Familie Cucumariidae (Ordnung Dendrochirota). 2 Teil: die Gattungen Cladodactyla, Hemioedema und Psolidiella. Mitt. Hamburg, zool. Mus. Inst. 55: Panning, A., Bemerkungen iiber die Holomurien-Familie Cucumariidae (Ordnung Dendrochirota). 3 Teil: die Gattung Pseudocnus. Mitt. Hamburg, zool. Mus. Inst. 60: Perrier, R., Holothuries. Expedition scientifique du "Travailleur" et du "Talisman" : , pis Paris.

33 MASSIN: HOLOTHURIANS OF THE TYRO MAURITANIA-II EXPEDITION 429 Rowe, F.W.E., A review of the family Holothuriidae (Holothuroidea, Aspidochirota). Bull. Brit. Mus. (nat. Hist.) Zool. 18 (4): Sibuet, M., Repartition et diversity des echinodermes (Holothurides et asterides) en zone profonde dans le Golfe de Gascogne. Deep-Sea Res. 24: Thandar, A.S., A new subspecies of Holothuria with a description of a new species from the south-east Atlantic Ocean. J. Zool. Lond. 215: Tortonese, E., Fauna dttalia. VI. Echinodermata: i-xiii, Bologna. Tyler, P.A., CM. Young, D.S.M. Billet & L.A. Giles, Pairing behaviour, reproduction and diet in the deep-sea holothurian genus Paroriza (Holothurioidea: Synallactidae). J. mar. biol. Ass. U.K. 72: Received: 20.U993 Accepted: 3.vi.l993 (after revision) Edited: J.C. den Hartog